1. Field of the Invention
This invention relates to metallurgical ladles and more particularly to an improved metallurgical ladle including a lining brick retaining band formed from ceramic material mounted on the top lip of the ladle shell.
2. Description of the Prior Art
Metallurgical ladles of the type used, for example, in the handling of molten steel have conventionally included a heavy refractory brick lining for the outer steel shell. The refractory brick lining must be able to withstand not only the extreme temperatures encountered in handling of the molten steel and in preheating, but must also have sufficient structural integrity to withstand stresses encountered during pouring, slag skimming and deslagging and any impact loads which may be encountered during handling generally.
In order to provide support for the brick lining at the top of a ladle, it has been conventional practice to provide an inwardly projecting flange, sometimes in the form of one leg of a structural angle welded to the ladle shell adjacent its open end, to overlie and structurally support the uppermost layer of lining brick. The structural steel flange is then protected from the extreme temperatures and from chemical and erosive effects of the slag on molten steel by a layer of castable refractory material. This refractory material conventionally has been retained in position by a plurality of metal anchor members welded to the inwardly projecting flange and extending from its surface to be embedded in the cast refractory layer.
Despite efforts to protect the lining brick retaining structure during use, this prior art system has not been entirely satisfactory since the known castable refractory materials only have a very short life, making it necessary to frequently repair or replace the cast overlay by a spraying or gunning operation to deposit magnesium oxide or other suitable material on the damaged area. This repair procedure is not only expensive because of the cost of the labor and materials, but also because of the necessity of taking a ladle out of service for repairs. Also, as the cast refractory continued to erode, the metal anchors are destroyed, thereby increasing the likelihood that the repair material will not be retained in position. Failure of the insulating cast material can quickly result in destruction of the structural steel retaining flange with the result that the retention support for the lining brick is lost and the brick will fall out during the ladle deslagging process. As a result, ladles employing the known lining brick retaining systems frequently have to be taken out of service for extended periods for repair.
The shortcomings of the prior art ladle brick retaining structures have been greatly magnified when the ladles are used in ladle metallurgy processes requiring a cover to be supported on the top of the ladle during processing. One such ladle metallurgy process now in wide use is disclosed in U.S. Pat. No. 4,560,405 and employs electrodes projecting through a ladle cover for supplying heat to the slag or flux layer during a desulfurizing process. The highly errosive action of the slag, and the extreme temperatures resulting from the electric arc heating process near the top of the ladle result in the slag attacking and rapidly eroding the known prior art lining brick retaining structures. Further, loads applied by the ladle cover required substantial strength as well as a relatively smooth top surface to support and maintain a seal with the ladle cover during such ladle metallurgy processes.